In 2011, the ITU-T officially began a project to define advanced high speed transmission on twisted pair cables to address high speed transmission on short loop lengths (<250 m) at speeds up to approximately 1 Gb/s aggregate (sum of upstream and downstream rates). The result of this study is ITU-T Recommendation G.9701 (i.e. the G.fast Recommendation or G.fast), which defines a transceiver specification based on time division duplexing (TDD) for the transmission of the downstream and upstream signals in a wide bandwidth of approximately 106 MHz and a symbol rate of approximately 48 kHz. This contrasts with prior standards such as VDSL2 having a 17.6 MHz bandwidth with a corresponding symbol rates of approximately 4 kHz and 30 MHz bandwidth with a corresponding symbol rate of 8 kHz.
In an effort to obtain power savings in a distribution point unit (DPU) with an option to operate with reverse power feed from the customer premises equipment (CPE), G.fast defines a scheme called discontinuous operation (DO). This allows transceivers on each link to “turn off” system processing to help scale the system power dissipation commensurate with the amount of data traffic being passed. By transmitting data in time slots when data is available and transmitting silence when there is no data available, the equipment power dissipation may be scaled directly with the available user payload data.
What is needed is an approach for managing DO in a G.fast or other TDD system that addresses various issues that are not contemplated or addressed by G.fast itself.